Construction work on Australia's biggest defence project has been further delayed amid budget cuts and a concern about the availability of skilled workers.

Defence Minister Stephen Smith says delivery of the $8 billion air warfare destroyer ships has been pushed out by up to nine months, which is on top of an estimated year-long delay announced mid-last year.

He says the move will result in a "relatively small" saving to the budget.

"Given that we're going through a very difficult budget time, a time of fiscal constraint, that the movement out of the forward estimate years of about $100 million does help us so far as our budget surplus and forward estimate requirements are concerned," Mr Smith told reporters in Adelaide.

Last year, work on aspects of the project was moved from a Melbourne shipyard to Adelaide, Newcastle and Spain because of concerns about delays.

Today, the Government celebrated a milestone with a keel-laying ceremony for the first of three air warfare destroyers, HMAS Hobart.

Mr Smith has described the latest delay as a "rescheduling" that was decided after extensive consultation with the industry.

"One of the things that has been a challenge for industry, and a challenge for Defence and the Defence Materiel Organisation and Navy, has been to try and get a steady and smooth flow of work.

"It will see a better retention of skills, a better workflow (and) secure work here (in Adelaide) until 2019."

Mr Smith says the new timetable will result in a more seamless flow of work between the air warfare destroyer project and the start of work on new submarines.

South Australian Premier Jay Weatherill says the delay would not prove negative for the local workforce.

"What we've seen is the avoidance of what was going to be a gap in the project and we're seeing a ramping up of employment here at Techport and instead of that falling off before we got to the Future Submarines project," he said.

"We now see a steady flow of work."

Commissioned

When the air warfare destroyer project was announced under the Howard government, the first ship was due to be delivered in late 2014, followed by the second and third ships in early 2016 and mid-2017 respectively.

With the latest delay, HMAS Hobart is now due to be commissioned in March 2016, followed by HMAS Brisbane in September 2017 and HMAS Sydney in March 2019.

But Mr Smith has been quick to reassure the community that Australia's naval capabilities will not be compromised by the most recent decision.

"There'll be no capability gap," Mr Smith said.

"The three air warfare destroyers will replace our current Adelaide frigates, and in the recent period we've seen... our four Adelaide class frigates be upgraded both in terms of radar and combat systems.

"When these come on stream, they will be the most effective air warfare destroyers that the Australian Navy has ever had."

But Coalition Defence spokesman David Johnston says Australia may now need to send warships to northern Australia to protect the nation's borders.

Senator Johnston says the Government should not be delaying the construction of warships, when thousands of asylum seekers are arriving in Australian waters.

"Well we might have to use them, we might have to use them in some shape or form on the maritime frontier," he said.

"We've got 8,000 people arriving every year on boats up in the north. To delay ships that we vitally need is just ridiculous.

"When you're building three very expensive boats, any delay in them means that capability has to be rearranged."

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